1. Field of the Invention
The invention relates to a liquid dispensing pump adapted for finger operation when mounted on a consumer-type container to provide a means for dispensing a liquid product from the container. It is a feature of the invention that the pump is so constructed as to produce sharp initiation and cut-off of dispensing flow during reciprocation of the pump plunger in order to avoid dribble on initiating and ending a pumping stroke. Such a pump is referred to herein as a "non-throttling" type.
2. Description of the Prior art
A number of non-throttling pump constructions have been proposed, and some have been used commercially. Those most relevant to the present invention are typified by the construction shown in U.S. Pat. Nos. 3,399,836 (Re. 28,366), 3,627,206, 3,746,260, 3,779,464, 3,923,250, 3,954,354, 4,025,046, 4,029,261 and 4,051,983. Pumps of the type in question involve some complexity of design and fabrication, arising from the conflicting requirements with regard to lowest manufacturing cost consistent with a design giving assurance of reliable dispensing function when operated by the consumer. Some of the problems encountered in attempting to meet these conflicting requirements include difficulty of minimizing the throttling effect during initiation and termination of a plunger stroke; assurred self-priming capability; matching oveall pump miniaturization to maximum requirements of dispensed liquid product. Many of the prior structures incorporate mechanical arrangements such as lost motion connections, differential frictional engagement between parts, and physical intricacy or smallness of certain parts, all of which lead to increased fabrication and assembly costs that tend to remove the final pump product from the category of being a component suitable for consumer-type disposable container use. However there is a large demand for dispensing pumps of this type, especially if they can meet the functional and economic criteria.